You can merge images by selecting the destination image you want to merge source images into.
AutoCAD Raster Design toolset merges your source images into a single destination image. The properties of your destination image, such as dpi and color depth will not change as a result of the merge. The merge will also respect any polygonal clip boundaries you have set, as well as brightness and contrast resolutions.
For example, if your source image has a value of 200 dpi, and your destination image has the value of 400 dpi, the destination image will retain the value of 400 dpi after you have performed a merge.
The destination image is expanded to encompass your source image(s). The background will be filled with the transparent color. You can change the transparent color in your image. For more information, see Transparent Color of an Image.